1. Field:
The present disclosure relates generally to measurements and, in particular, to measuring objects. Still more particularly, the present disclosure relates to a method and apparatus for identifying coordinates of objects in images.
2. Background:
Photogrammetry is a three-dimensional coordinate measurement technique. This technique uses photographs as a medium to make measurements. With photogrammetry, triangulation is used to identify coordinates of objects. Images of an object are generated from at least two different locations to points on an object. Each point on the object is a location on the object. The lines from these locations to the points on the object may also be referred to as lines of sight or rays. These lines of sight may be processed mathematically to identify three-dimensional coordinates for the points on the object.
With photogrammetry, images are generated using camera systems. Typically, the camera systems have two or more cameras at different locations. The cameras are located at the locations from which lines of sight are identified to point on an object. With the images generated by the cameras, three-dimensional information, such as a three-dimensional location of points, is identified.
The mathematic processing in photogrammetry involves using triangulation to identify three-dimensional coordinates for points in the images. The different cameras provide lines of sight to the different points that may converge in space. With images of an object containing the points, a line of sight may be identified from each camera to the points on the object. If the location of the camera and the aiming direction is known, the lines of sight may be used to identify three-dimensional coordinates for each point.
In generating images for identifying coordinates for points on an object, the camera system is positioned such that any given point on the object can be seen by both of the cameras in the camera system at the point in time the image of the object is generated. Further, additional images may be generated for use in increasing accuracy of measurements.
When points on an object are hidden from the view of the camera system, measurements of these points cannot be made. In some cases, not all of the points of interest for measurements on an object can be seen from the camera system from any one position.
One solution involves moving the camera system to another location such that the cameras are positioned to generate images of the points that were hidden from view in the first location. Although this type of process provides coordinates for the desired points, additional time and calculations are needed when the camera system is moved from one location to another location.
Therefore, it would be advantageous to have a method and apparatus that takes into account at least one of the issues discussed above, as well as other possible issues.